Method of controlling mobile communication system, control device, and mobile communication system

ABSTRACT

A mobile communication system controls switching a transmission diversity system for each channel, and improves the quality of the channel. When the channel type in an uplink is a channel for transmitting voice, open loop transmission diversity is used (steps S 1 →S 3 ). When the channel type in an uplink is a channel for transmitting a packet, closed loop transmission diversity is used (steps S 1 →S 2 ). Since the open loop transmission diversity or the closed loop transmission diversity which ever is more appropriate can be used, a transmission diversity system can be appropriately switched for each channel, thereby improving the quality of the channel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of controlling a mobilecommunication system, a control device, and a mobile communicationsystem, and more specifically to the control of a transmission diversitysystem in the mobile communication system.

2. Description of the Related Art

Generally, in a mobile communication system, a momentary levelfluctuation can occur on a receiving side due to multi-path fading,etc., thereby greatly degrading the uplink reception characteristic in aradio base station and the downlink reception characteristic in a mobilestation. There are the technologies for reducing the degradation such asthe reception diversity for reception using a plurality of antennas on areceiving side, the transmission diversity for transmission using aplurality of antennas on a base station side, etc. Since thetransmission diversity is a method for reducing the level fluctuationwithout enlarging the circuit (or increasing the number of antennas) onthe receiving side, it is common to apply it in downlink mainly. Forexample, according to “3GPP RAN TS25.214 V3. c. O, March 2003” (hereinafter referred to as non-patent document 1), there are two types oftransmission diversity, that is, open loop transmission diversity (STTDin the non-patent document 1) for obtaining a diversity effect byperforming a predetermined symbol conversion using each antenna of abase station, and closed loop transmission diversity (closed loop mode 1and closed loop mode 2 in the non-patent document 1) for allowing amobile station to transmit a feedback command such that the optimumpattern can be obtained for the amplitude and the phase of signals fromeach antenna, and allowing a base station to determine the transmissionphase and amplitude according to the command.

FIG. 8 shows the concept of the open loop transmission diversity (STTD).FIG. 9 shows the concept of the control of closed loop transmissionpower (closed loop mode 1 or closed loop mode 2).

The STTD as an example of the open loop transmission diversity isexplained below by referring to FIG. 8. As shown in FIG. 8, in the STTD,an STTD encoder 3, an antenna Ant 1, and an antenna Ant 2 are providedon the base station side, and an antenna MS Ant and an STTD decoder 4are provided on the mobile station side.

The STTD encoder shown in FIG. 8 calculates the complex conjugate of anodd symbol, multiplies an even symbol by a minus sign after thecalculation of the complex conjugate, inverts the odd symbol and theeven symbol, and performs transmission.

When α₁ and α₂ respectively indicate the fading vector of a transmissionline from the antenna 1 (first antenna) to the mobile station, and thefading vector of a transmission line from the antenna 2 (second antenna)to the mobile station, the signals received by the mobile station can beexpressed as follows. For simplicity, the noise is not considered inthis example.r ₁=α₁ S ₁−α₂ S ₂*r ₂=α₁ S ₂+α₂ S ₁*  (math 1)

This is calculated in a STTD decoder as follows, and the calculationresult Output is output.Output 1=α₁ *r ₁+α₂ r ₂*=(|α₁|²+|α₂|²)S ₁Output 2=α₂ *r ₂+α₁ r ₁*=(|α₁|²+|α₂|²)S ₂  (math 2)

Thus, the fading from the antennas 1 and 2 can be combined at themaximum rate.

The closed loop mode 1 is explained below as an example of the closedloop transmission diversity by referring to FIG. 9. In the closed loopmode 1 as shown in FIG. 9, in the closed loop mode 1, multipliers 5 and6, an FBI decoder 7, and antennas Ant land 2 are provided on the basestation side. The antenna MS Ant, a data decoder 8, and a weightselector 9 are provided on the mobile station side. The multiplicationweight multiplied in the multipliers 5 and 6 is transmitted from themobile station side over a dedicated uplink channel, and is decoded inthe FBI decoder 7.

The W₁ shown in FIG. 9 indicates a multiplication weight of signalstransmitted from the antenna Ant 1 by which transmission signals aremultiplied, and the W₂ indicates a multiplication weight of signalstransmitted from the antenna Ant 2 by which transmission signals aremultiplied. The weight has the following pattern.(W ₁ ,W ₂)=(1,e×p(jφ))  (math 3)

φ={π/4, 3π/4, 5π/4, 7π/4}

FIG. 10 shows a phase plane of a pattern of the weight W₂. The receivedsignals are expressed by the following equation.r=((α₁ W ₁+α₂ W ₂)S  (math 4)

In the case of the closed loop mode 1, as shown by the (math 3) above,W₁ is fixed to 1. Therefore, in the mobile station, W₂ is determined tomaximize α₁W₁+α₂W₂, a positive or negative value of I-axis component ofW₂ is specified by an odd time slot, and a positive or negative value ofQ-axis component of W₂ is specified by an even time slot. In the basestation, transmission is performed using the latest I-axis and Q-axiscomponents.

The time slot is constituted by a dedicated physical data channel(DPDCH) and a dedicated physical control channel (DPCCH) as shown inFIG. 10. In FIG. 10, the dedicated physical data channel is constitutedby the data unit (Data) of N_(data)-bit. The dedicated physical controlchannel is constituted by an N_(pilot)-bit pilot unit (Pilot), anN_(TFCI)-bit TFCI (transport format combination indicator) unit, anN_(FBI)-bit FBI (feedback information) unit, and an N_(TPC)-bit TPCunit. The weight is updated using an FBI unit (herein after referred toas an FBI bit) assigned to the DPCCH.

In the closed loop data decoder, the following calculation is performedto obtain the original signals. In the equation the noise component isomitted for simplicity.Output 2=(α₁ W ₁+α₂ W ₂)r=|α ₁ W ₁+α₂ W ₂|² S  (math 5)

The received signals can obtain a gain (beam forming gain) for in-phase,and a larger gain can be ideally obtained as compared with the open looptransmission diversity. However, the above-mentioned FBI bit canerroneously be detected in uplink, and the more states in which theweight used in the base station is different from the weight assumed bythe mobile station occur, the more easily the quality is degraded.

To reduce the degradation by the FBI bit error, the mobile station canperform antenna verification to estimate the weight used in the basestation with higher accuracy. The Annex A of the non-patent document 1shows an example of the method. As shown in the above-mentioned example,the determination accuracy is enhanced by assuming a BER (bit errorrate) in the uplink of the FBI bit, and including a presumedprobability. However, although the antenna verification is correctlyperformed, there occur the degradation in beam forming gain due to anFBI bit error, and an antenna verification error by mistakenlyestimating the weight used by the base station. Therefore, when the FBIbit error rate increases, it is stated that the gain of the closed looptransmission diversity is degraded.

As a conclusion, when the FBI bit error rate is low in the uplink fromthe mobile station to the base station, a larger gain is obtained by theclosed loop transmission diversity than by the open loop transmissiondiversity, but when the FBI bit error rate in the uplink is high, a gaincan be more stably obtained by the open loop transmission diversity thanby the closed loop transmission diversity.

The FBI bit error rate depends on the transmission rate of the channelin the uplink, a spreading factor, a transmission time interval(transmission time interval: herein after referred to as a TTI forshort), the number of FBI bits, a target error rate and a slot format.Normally, when the transmission rate is high, the FBI bit error rate islow. When the transmission rate is low, the FBI bit error rate is high.An FBI bit is mapped over the dedicated physical control channel DPCCH(dedicated physical control channel), not over the dedicated physicaldata channel DPDCH (dedicated physical data channel). Therefore, when acomparison is made between a low amplitude ratio of the DPCCH to theDPDCH and a high amplitude ratio, the FBI bit error rate is lower whenthe amplitude ratio is high.

JP2002-64414A (herein after referred to as patent document 1) describesthe technology of applying the closed loop transmission diversityaccording to the application request information when a predeterminedcondition is satisfied, for example, when there is no fluctuation ofradio transmission line characteristic, etc.

SUMMARY OF THE INVENTION

As described above, the closed loop transmission diversity can obtain alarger gain than the open loop transmission diversity when an FBI biterror rate is low. However, the closed loop transmission diversity canobtain a smaller gain than the open loop transmission diversity when anFBI bit error rate is high.

The FBI bit error rate depends on the channel type of an uplink, or thetransmission rate, the spreading factor, the TTI, the number of FBIbits, the target error rate, and the slot format. Normally, when atransmission rate is high, or when the power of the DPCCH is high, theFBI bit error rate becomes low. When the transmission rate is low, orwhen the power of the DPCCH is low, the FBI bit error rate becomes high.

The present invention has been developed to solve the above describedproblems of the conventional technology, and the object of the presentinvention is to provide a method of controlling a mobile communicationsystem, a control device, and a mobile communication system capable ofimproving the quality of a channel by performing control of switching atransmission diversity system for each channel by applying the closedloop transmission diversity to a channel estimated to have a low FBIerror rate in an uplink, and applying the open loop transmissiondiversity to a channel estimated to have a high FBI error rate.

The method of controlling a mobile communication system according toclaims of the present invention includes a radio base station to whichtransmission diversity of performing radio transmission using aplurality of antennas is applied, and a mobile station for communicatingwith the radio base station. A transmission diversity system isdetermined according to the information about a channel in an uplinkfrom the mobile station to the radio base station. Thus, thetransmission diversity system can be appropriately switched for eachchannel, thereby improving the quality of the channel.

In the transmission control method for the mobile communication systemaccording to claims of the present invention, the information about thechannel in the uplink is a channel type, open loop transmissiondiversity is used when the channel type refers to a channel fortransmitting voice, and closed loop transmission diversity is used whenthe channel type refers to a channel for transmitting a packet. Thus,the open loop transmission diversity or the closed loop transmissiondiversity which ever is more appropriate can be used.

In the method of controlling a mobile communication system according toclaims of the present invention, the information about the channel inthe uplink is a transmission rate of a channel in an uplink, anamplitude ratio of a control channel to a data channel, a transmissiontime interval, a target error rate, and a slot format, based on at leastone of which a transmission diversity system is determined. Thus, thetransmission diversity system can be more appropriately determined.

In the method of controlling a mobile communication system according toclaims of the present invention, the transmission diversity systemcontrol means uses open loop transmission diversity when thetransmission rate of the channel in the uplink is low, and uses closedloop transmission diversity when the transmission rate of the uplink ishigh. Thus, the open loop transmission diversity or the closed looptransmission diversity which ever is more appropriate can be used.

In the method of controlling a mobile communication system according toclaims of the present invention, the information about the channel inthe uplink is a signal-to-interference power ratio of a physical controlchannel of the uplink, and a signal-to-interference power ratio of pilotsignals (for example, the pilot unit shown in FIG. 11) based on at leastone of which a transmission diversity system is determined. Thus, thetransmission diversity system can be more appropriately determined basedon the SIR which changes from moment to moment.

The control device according to claims of the present invention controlsthe execution of transmission diversity of a radio base station forperforming wireless transmission with a mobile station using a pluralityof antennas, and includes transmission diversity system control meansfor determining a transmission diversity system according to theinformation about a channel in an uplink from the mobile station. Usingthe control device with the above-mentioned configuration, atransmission diversity system can be appropriately switched for eachchannel, thereby improving the quality of a channel.

In the control device according to claims of the present invention, theinformation about the channel in the uplink is a channel type, and thetransmission diversity system control means uses open loop transmissiondiversity when the channel type refers to a channel for transmittingvoice, and uses closed loop transmission diversity when the channel typerefers to a channel for transmitting a packet. With the control device,the open loop transmission diversity or the closed loop transmissiondiversity which ever is more appropriate can be used.

In the control device according to claims of the present invention, theinformation about the channel in the uplink is a transmission rate of achannel in the uplink, an amplitude ratio of a control channel to a datachannel, a transmission time interval, a target error rate, and a slotformat, based on at least one of which the transmission diversity systemcontrol means determines a transmission diversity system. With theconfiguration of the control device, a transmission diversity system canbe more appropriately determined.

In the control device according to claims of the present invention, thetransmission diversity system control means uses open loop transmissiondiversity when the transmission rate of the channel in the uplink islow, and uses closed loop transmission diversity when the transmissionrate of the uplink is high. With the control device, the open looptransmission diversity or the closed loop transmission diversity whichever is more appropriate can be used.

In the control device according to claims of the present invention, theinformation about the channel in the uplink is a signal-to-interferencepower ratio (herein after referred to as a SIR) of a physical controlchannel of the uplink, and a signal-to-interference power ratio of pilotsignals (for example, the pilot unit shown in FIG. 11), based on atleast one of which the transmission diversity system control meansdetermines a transmission diversity system. Thus, the transmissiondiversity system can be more appropriately determined based on the SIRwhich changes from moment to moment.

The mobile communication system according to claims of the presentinvention includes a mobile station, a radio base station for performingwireless transmission to the mobile station using a plurality ofantennas, and a radio network controller for controlling the mobilestation and the radio base station, and controls execution oftransmission diversity of the radio base station. The control deviceaccording to the claims is provided for at least one of the mobilestation, the radio base station, and the radio network controller. Withthe configuration of the mobile communication system, a transmissiondiversity system can be more appropriately switched for each channel,thereby improving the quality of a channel.

As explained above, the quality of the downlink, for example, the BLER(block error rate), and a required transmission power can be improvedaccording to the present invention by determining the transmissiondiversity system based on the channel type of an uplink, thetransmission rate, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of the configuration of themobile communication system according to a mode for embodying thepresent invention;

FIG. 2 is a block diagram showing the function of the configurationexample of the radio network controller 30 shown in FIG. 1;

FIG. 3 is a flowchart of the transmission diversity system depending onthe channel type;

FIG. 4 is a flowchart of the transmission diversity system depending onthe transmission rate of the uplink;

FIG. 5 is a flowchart of the transmission diversity system depending onthe amplitude ratio of the control channel;

FIG. 6 is a flowchart of the transmission diversity system depending onthe transmission rate and the amplitude ratio;

FIG. 7 is a flowchart of the transmission diversity system depending onthe SIR;

FIG. 8 shows the concept of the open loop transmission diversity (STTD);

FIG. 9 shows the concept of the closed loop transmission diversity(closed loop mode 1 or 2);

FIG. 10 shows the phase pattern of the weight W₂; and

FIG. 11 shows the slot format of the DPDCH and the DPCCH of the uplink.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The modes for embodying the present invention are described below byreferring to the attached drawings. In the following explanation, acomponent commonly used in other figures is identified by the samereference numeral.

(Mobile Communication System)

The modes for embodying the present invention are explained below byreferring to the attached drawings. FIG. 1 shows an example of thesystem configuration of the mobile communication system to which thepresent invention is applied. As shown in FIG. 1, it is assumed that themobile communication system includes a mobile station 10, a base station20 for performing wireless communication with the mobile station 10using a plurality of antennas, and a radio network controller 30 forcontrolling the mobile station 10 and the base station 20.

The present invention controls switching the transmission diversitysystem of a downlink depending on the channel type of an uplink when thetransmission diversity is applied in the downlink, and the descriptionsof the components not related to the present invention are omitted.

FIG. 2 is a block diagram showing the function of the configurationexample of the radio network controller 30 according to the mode forembodying the present invention. As shown in FIG. 2, the radio networkcontroller 30 includes a channel setting unit 31 and a transmissiondiversity system control unit 34 for determining the transmissiondiversity system. The channel setting unit 31 includes an uplink channelsetting unit 32 and a downlink channel setting unit 33. FIG. 2 showsonly the portion for setting a radio channel and the portion fordetermining the transmission diversity system related to the presentmode for embodying the present invention in the radio network controller30.

In this example, the transmission diversity system control unit 34 isprovided in the radio network controller 30, but the transmissiondiversity system can also be determined by providing the transmissiondiversity system control unit 34 in the mobile station 10 or the basestation 20.

(Channel Setting Unit)

The channel setting unit 31 acquires the information about the servicetype provided for the mobile station 10 from a core network such as theinformation about voice communications, a television telephone, packetcommunications, etc., and sets a parameter of an uplink channel and aparameter of a downlink channel respectively in the uplink channelsetting unit 32 and the downlink channel setting unit 33 in the channelsetting unit 31.

The parameter refers to, for example, a transmission rate and aspreading factor, a TTI, the number of FBI bits, a target error rate,the amplitude ratio of the DPCCH to the DPDCH (uplink only), a slotformat, etc. The channel setting unit 31 notifies the transmissiondiversity system control unit 34 of the parameter of the uplink set asdescribed above, that is, a transmission rate and a spreading factor, aTTI, a target error rate, the amplitude ratio of the DPCCH to the DPDCH(uplink only), a slot format, etc.

The channel setting unit 31 can inform about not only theabove-mentioned parameter, but also the service type, for example,voice, a television telephone, packet communication, etc. to betransmitted through the uplink.

(Transmission Diversity System Control Unit)

The transmission diversity system control unit 34 receives from thechannel setting unit 31 the parameter of the uplink, that is, atransmission rate and a spreading factor, a TTI, a target error rate,the amplitude ratio of the DPCCH to the DPDCH, a slot format, etc., or achannel type of the uplink. Then, it determines the transmissiondiversity system based on at least one of the transmission rate and thespreading factor, the TTI, the target error rate, the amplitude ratio ofthe DPCCH to the DPDCH, the slot format, etc., or a channel type of theuplink. The determined transmission diversity system is transmitted tothe mobile station 10 and the base station 20.

For example, the transmission diversity system control unit 34 candetermine that the transmission diversity system is open looptransmission diversity when the channel of the uplink is a channel fortransmitting voice signals, and can determine that the transmissiondiversity system is closed loop transmission diversity when the channeltype of the uplink is a channel for transmitting packet signals.

For example, the transmission diversity system control unit 34 candetermine that the transmission diversity system is open looptransmission diversity when the transmission rate of the channel of theuplink is equal to or less than 32 kbps, and can determine that thetransmission diversity system is closed loop transmission diversity whenthe transmission rate of channel type of the uplink is not equal to orless than 32 kbps.

For example, it also can determine that the transmission diversitysystem is open loop transmission diversity when the amplitude ratio ofthe DPCCH to the DPDCH of the uplink is lower than 12/15, and candetermine that the transmission diversity system is closed looptransmission diversity when the amplitude ratio of the DPCCH to theDPDCH of the uplink is equal to or higher than 12/15.

It also can determine the transmission diversity system based on boththe transmission rate and the amplitude ratio of the DPCCH to the DPDCHof the uplink. For example, it can determine that the transmissiondiversity system is open loop transmission diversity when thetransmission rate is equal to or less than 32 kbps and the amplituderatio of the DPCCH to the DPDCH of the uplink is lower than 12/15, candetermine that the transmission diversity system is closed looptransmission diversity when the transmission rate is equal to or lessthan 32 kbps and the amplitude ratio of the DPCCH to the DPDCH of theuplink is equal to or higher than 12/15, and can constantly determinethat the transmission diversity system is closed loop transmissiondiversity when the transmission rate is more than 32 kbps.

The transmission diversity system control unit 34 can determine thetransmission diversity system based on the SIR (Signal to InterferenceRatio) of the physical control channel of the uplink, or the SIR valueof the pilot signals. That is, if the SIR value is equal to or higherthan a predetermined threshold, it can be determined that thetransmission diversity system is closed loop transmission diversity. Ifit is lower than the predetermined threshold, it can be determined thatthe transmission diversity system is open loop transmission diversity.Thus, the transmission diversity system can be more appropriatelydetermined based on the SIR which changes from moment to moment. The SIRvalue is measured by the base station 20, and the measurement result canbe notified to the transmission diversity system control unit 34 in theradio network controller 30. Otherwise, in the base station 20, thetransmission diversity system can be determined from the SIR, and thedetermination result can be notified to the radio network controller 30.

In the explanation above, the transmission diversity system control unit34 determines the transmission diversity system using the channel typeof the uplink, the transmission rate, etc. However, since the channelsof the uplink and the downlink are typically symmetric, the transmissiondiversity system can be determined using the channel type of thedownlink, the transmission rate, etc. instead of the channel type of theuplink, the transmission rate, etc.

(Communication Control Method for Mobile Communication System)

Next, the communication control method for the mobile communicationsystem according to the present invention is explained by referring tothe flowchart shown in FIG. 3.

(Transmission Diversity System Depending on Channel Type)

First, in step S1 shown in FIG. 3, it is determined whether or not thechannel of the uplink transmits voice signals. If it is determined thatthe channel transmits voice signals, then control is passed to step S3.If it is determined that the channel does not transmit voice signals,then control is passed to step S2.

In step S2, it is determined that the closed loop transmission diversityis applied to the channel as a transmission diversity system.

In step S3, it is determined that the open loop transmission diversityis applied to the channel as a transmission diversity system.

(Transmission Diversity System Depending on Transmission Rate of Uplink)

An other mode of the receiving method using the reception deviceaccording to the present invention is described below by referring tothe flowchart shown in FIG. 4.

First, in step S11 shown in FIG. 4, it is determined whether or not thetransmission rate of the uplink is equal to or less than 32 kbps. If itis determined that the transmission rate of the uplink is equal to orless than 32 kbps, then control is passed to step S13. If it isdetermined that the transmission rate of the uplink is not equal to orless than 32 kbps, then control is passed to step S12.

In step S12, it is determined that the closed loop transmissiondiversity is applied to the channel as a transmission diversity system.

In step S13, it is determined that the open loop transmission diversityis applied to the channel as a transmission diversity system.

The transmission diversity system can be determined by discriminatingwhether or not the transmission rate of the uplink is equal to or lessthan 32 kbps. However, it also can be determined depending on thetransmission rate other than 32 kbps.

(Transmission Diversity System Depending on Amplitude Ratio of ControlChannel)

Another mode of the receiving method using the reception deviceaccording to the present invention is described below by referring tothe flowchart shown in FIG. 5.

First, it is determined in step S21 shown in FIG. 5 whether or not theamplitude ratio of the DPCCH to the DPDCH of the uplink is lower than12/15. If it is determined that the amplitude ratio of the DPCCH to theDPDCH of the uplink is lower than 12/15, then control is passed to stepS23. If it is determined that the amplitude ratio of the DPCCH to theDPDCH of the uplink is not lower than 12/15, then control is passed tostep S22.

In step S22, it is determined that the closed loop transmissiondiversity is applied to the channel as a transmission diversity system.

In step S23, it is determined that the open loop transmission diversityis applied to the channel as a transmission diversity system.

In the process above, the transmission diversity system is determineddepending on whether or not the amplitude ratio of the DPCCH to theDPDCH of the uplink is lower than 12/15, but it also can be determineddepending on the value other than 12/15.

(Transmission Diversity System Depending on the Transmission Rate andthe Amplitude Ratio)

An other mode of the receiving method using the reception deviceaccording to the present invention is described below by referring tothe flowchart shown in FIG. 6.

First, in step S31 shown in FIG. 6, it is determined whether or not thetransmission rate of the uplink is equal to or less than 32 kbps. If itis determined that the transmission rate of the uplink is equal to orless than 32 kbps, then control is passed to step S33. If it isdetermined that the transmission rate of the uplink is not equal to orless than 32 kbps, then control is passed to step S32.

It is determined in step S33 whether or not the amplitude ratio of theDPCCH to the DPDCH of the uplink is lower than 12/15. If it isdetermined that the amplitude ratio of the DPCCH to the DPDCH of theuplink is lower than 12/15, then control is passed to step S34. If it isdetermined that the amplitude ratio of the DPCCH to the DPDCH of theuplink is not lower than 12/15, then control is passed to step S32.

In step S32, it is determined that the closed loop transmissiondiversity is applied to the channel as a transmission diversity system.

In step S34, it is determined that the open loop transmission diversityis applied to the channel as a transmission diversity system.

(Transmission Diversity System Depending on SIR)

An other mode of the receiving method using the reception deviceaccording to the present invention is described below by referring tothe flowchart shown in FIG. 7.

First, it is determined in step S41 shown in FIG. 7 whether or not theSIR value of the physical control channel of the uplink is equal to orhigher than 3 dB. If it is determined that the SIR value is equal to orhigher than 3 dB, control is passed to step S43. If it is determinedthat the SIR value is not equal to or higher than 3 dB, control ispassed to step S42.

In step S43, it is determined that the closed loop transmissiondiversity is applied to the channel as a transmission diversity system.

In step S42, it is determined that the open loop transmission diversityis applied to the channel as a transmission diversity system.

In the above-mentioned receiving method, the transmission diversitysystem can be more appropriately determined based on the SIR whichchanges from moment to moment. In the explanation above, thetransmission diversity system is determined based on the SIR of thephysical control channel of the uplink, but it also can be determinedbased on the SIR value of the pilot signals (for example, the pilot unitshown in FIG. 11).

CONCLUSION

As explained above, according to the mode for embodying the presentinvention, the transmission diversity system can be determined based onthe channel type of the uplink, the transmission rate, etc. As a result,an appropriate transmission diversity system can be applied to eachchannel. Therefore, an error rate of each channel can be reduced. Whenthe transmission power control is performed, the transmission power tobe assigned to the channel can be reduced.

For example, since a channel for transmitting a packet generally has ahigher transmission rate than a channel for transmitting voice, it canbe estimated that an FBI bit error rate is high in the case of thechannel for transmitting voice, and it is low in the case of the channelfor transmitting a packet.

Therefore, the open loop transmission diversity is applied to a channelfor transmitting voice while the closed loop transmission diversity isapplied to a channel for transmitting a packet, thereby improving theradio characteristic of the channel.

Also, the embodiment described above relates to a wideband Code DivisionMultiple Access (WCDMA) system in the 3GPP (3rd Generation PartnershipProject). However, the present invention is not limited to the WCDMA,but can be applied to another communication system using transmissiondiversity in a mobile communication system, to the MIMO (multiple inputmultiple output) system using feedback information, and to an adaptivearray antenna system.

The present invention can be used in controlling the transmissiondiversity system in a mobile communication system.

1. A method of controlling a mobile communication system, comprising aradio base station to which transmission diversity of performing radiotransmission using a plurality of antennas is applied, and a mobilestation for communicating with the radio base station, wherein atransmission diversity system is determined according to informationabout a channel in an uplink from the mobile station to the radio basestation and wherein the information about the channel in the uplink is achannel type, open loop transmission diversity is used when the channeltype refers to a channel for transmitting voice, and closed looptransmission diversity is used when the channel type refers to a channelfor transmitting a packet.
 2. The method of controlling a mobilecommunication system according to claim 1, wherein the information aboutthe channel in the uplink is a signal-to-interference power ratio of aphysical control channel of the uplink, and a signal-to-interferencepower ratio of pilot signals based on at least one of which atransmission diversity system is determined.
 3. A method of controllinga mobile communication system, comprising a radio base station to whichtransmission diversity of performing radio transmission using aplurality of antennas is applied, and a mobile station for communicatingwith the radio base station, wherein a transmission diversity system isdetermined according to information about a channel in an uplink fromthe mobile station to the radio base station, wherein the informationabout the channel in the uplink is a transmission rate of a channel inan uplink, an amplitude ratio of a control channel to a data channel, atransmission time interval, a target error rate, and a slot format,based on at least one of which a transmission diversity system isdetermined, and wherein the transmission diversity system control meansuses open loop transmission diversity when the transmission rate of thechannel in the uplink is low, and uses closed loop transmissiondiversity when the transmission rate of the uplink is high.
 4. A controldevice which controls execution of transmission diversity of a radiobase station for performing wireless transmission with a mobile stationusing a plurality of antennas, comprising transmission diversity systemcontrol means for determining a transmission diversity system accordingto information about a channel in an uplink from the mobile station,wherein the information about the channel in the uplink is a channeltype, and the transmission diversity system control means uses open looptransmission diversity when the channel type refers to a channel fortransmitting voice, and uses closed loop transmission diversity when thechannel type refers to a channel for transmitting a packet.
 5. Thecontrol device according to claim 4, wherein the information about thechannel in the uplink is a signal-to-interference power ratio of aphysical control channel of the uplink, and a signal-to-interferencepower ratio of pilot signals, based on at least one of which thetransmission diversity system control means determines a transmissiondiversity system.
 6. A mobile communication system which comprises amobile station, a radio base station for performing wirelesstransmission to the mobile station using a plurality of antennas, and aradio network controller for controlling the mobile station and theradio base station, and controls execution of transmission diversity ofthe radio base station, wherein the control device according to claim 5is provided for at least one of the mobile station, the radio basestation, and the radio network controller.
 7. A mobile communicationsystem which comprises a mobile station, a radio base station forperforming wireless transmission to the mobile station using a pluralityof antennas, and a radio network controller for controlling the mobilestation and the radio base station, and controls execution oftransmission diversity of the radio base station, wherein the controldevice according to claim 4 is provided for at least one of the mobilestation, the radio base station, and the radio network controller.
 8. Acontrol device which controls execution of transmission diversity of aradio base station for performing wireless transmission with a mobilestation using a plurality of antennas, comprising transmission diversitysystem control means for determining a transmission diversity systemaccording to information about a channel in an uplink from the mobilestation, wherein the information about the channel in the uplink is atransmission rate of a channel in the uplink, an amplitude ratio of acontrol channel to a data channel, a transmission time interval, atarget error rate, and a slot format, based on at least one of which thetransmission diversity system control means determines a transmissiondiversity system, and wherein the transmission diversity system controlmeans uses open loop transmission diversity when the transmission rateof the channel in the uplink is low, and uses closed loop transmissiondiversity when the transmission rate of the uplink is high.
 9. A mobilecommunication system which comprises a mobile station, a radio basestation for performing wireless transmission to the mobile station usinga plurality of antennas, and a radio network controller for controllingthe mobile station and the radio base station, and controls execution oftransmission diversity of the radio base station, wherein the controldevice according to claim 8 is provided for at least one of the mobilestation, the radio base station, and the radio network controller.